[llvm-dev] Flang landing in the monorepo - next Monday!

Tue Jan 7 17:29:25 PST 2020

Hi Hal,

On Tue, Jan 7, 2020 at 3:38 PM Finkel, Hal J. via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

>
> On 1/7/20 4:38 PM, Doerfert, Johannes via llvm-dev wrote:
>
> On 01/07, David Blaikie via llvm-dev wrote:
>
> Hey Peter - would you be able to link to/describe the history on this
> process/decision. I can find one old thread where this was first proposed (http://lists.llvm.org/pipermail/llvm-dev/2019-February/130497.html ) with
> some general positive responses and a lot of questions.
>
> I see there's a flang-dev list, though I'm not sure where code review is
> happening (is there flang-commits or equivalent?) as there's not much
> chatter on the mailing list that I can see.
>
> There is a flang-commits. We have everything set up to use Phabricator
> as MLIR did.
>
>
> & I'm a bit concerned about flang, already a project with no LLVM API
> usage, it seems, and a community that doesn't currently look like it has
> much overlap with the LLVM developer community (a very rough glance at
> flang-dev participants, but I could be wrong - the LLVM community is large,
> to be sure) - I'm concerned that this might create a not very well
> integrated community, as we saw in the past with lldb, for instance.
>
> I think I mentioned this before but some people are waiting for the move
> to be able to actually participate in the Flang development. So the
> current github contributions do not necessarily reflect the LLVM
> developers that will be involved.
>
>
> I'll add to this that a number of us who have been involved with LLVM for
> a long time are involved in guiding the Flang project. While it's certainly
> true that a few of the people working hard on Flang are new to the LLVM
> community, there is a reasonable overlap with the existing LLVM community
> in the overall effort.
>
>
> On flang-dev [0] we have long term LLVM developers and people that join
> the LLVM developers community with the merge of Flang but even those
> already actively participated at the LLVM-Dev!
>
> The API usage is a valid concern, among others, which will require code
> changes in the near future.
>
> [0] http://lists.llvm.org/pipermail/flang-dev/2019-December/author.html
>
>
> The other thing that I'll add here is that the existing Flang development
> has been broad and not deep - the development started with the lexical
> analysis (and preprocessor), then the semantic analysis, and so on. It is
> only very recently that any work on actual code generation has begun, and
> there, the initial focus has been on targeting LLVM via MLIR. I'm not
> saying that there aren't more places to use LLVM APIs (e.g., filesystem
> abstractions, ADT, etc.) -- there are -- but that's something we're
> planning to improve over time.
>
> At a high level, however, the whole point of this Flang project is produce
> an LLVM-community-integrated Fortran frontend for LLVM. The current
> developers of the project, which is a growing community, are committed to
> realizing that outcome and are open to feedback on code structure, API
> usage, and other aspects of integrating with the rest of the LLVM project.
>
I added you to the original thread when I was replying because I knew you
were around this effort, it might be nice to see if you can respond to the
other thread too.

A lot of my concerns are echoed by David here and I have additional
concerns as well. I don't think the project is ready for inclusion into the
main llvm tree as I don't see the point right now. There's nothing llvm
about it.

-eric

>  -Hal
>
>
> Thanks,
>   Johannes
>
>
> On Tue, Jan 7, 2020 at 6:04 AM Peter Waller via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>
>
> Hi All,
>
> As discussed before Christmas, this is a reminder that we intend to
> merge flang on the 13th January (next Monday) before the llvm-10 branch.
> At the moment I'm proposing to do it at 10am GMT. I can be flexible on
> this point if it requires close coordination with anyone in another
> timezone, just let me know.
>
> Previous discussion was in [llvm-dev] Flang landing in the monorepo<http://lists.llvm.org/pipermail/llvm-dev/2019-December/137661.html> <http://lists.llvm.org/pipermail/llvm-dev/2019-December/137661.html>.
>
> The current plan of action is summarized at<https://github.com/flang-compiler/f18/issues/876> <https://github.com/flang-compiler/f18/issues/876>.
>
> The result will look a lot like the recent MLIR merge from 24th Dec:<https://github.com/llvm/llvm-project/commits/0f0d0ed1c78> <https://github.com/llvm/llvm-project/commits/0f0d0ed1c78>, commit
> 0f0d0ed1c78 in the llvm-project monorepo.
>
> Once it is done I'll mail the list. If you want to coordinate with me,
> please get in touch.
>
> Regards,
>
> - Peter
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>
> --
> Hal Finkel
> Lead, Compiler Technology and Programming Languages
> Leadership Computing Facility
> Argonne National Laboratory
>
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